Numerous well known cutting mechanisms exist in the area of cutting with counter-blades. With the majority of these curbing mechanism there is a frictional connection between the moving blades and the counter-blades.
The energy requirement for known cutting mechanisms of this type is high, because of the friction. Beyond this the wear of operating components is of a significant magnitude.
Besides this, the speed of revolutions of the rotary discs to which the blades are mounted, is restricted due to the frictional connection between the counter-blades and the moving blades. The moving blades can only rotate at a peripheral speed of about 3-6 m/sec. A result of this is that the cutting, guiding and collection of the pieces of vegetation, can only be carried out at a low work rate.
A further disadvantage of the previously listed cutting mechanisms is that due to the high energy demand, neither accumulators nor low voltage electric motors can be utilized as sources of energy for the drives of said cutting mechanisms.
A large section of these cutting mechanisms is made up of the alternating cutting mechanisms, such as for example the U.S. Pat. No. 4,881,363. The energy requirement for such a cutting mechanism, which is necessary, in part for the frictional losses and in part for the transmission, assumes the utilization of an internal combustion engine. The utilization of such an internal combustion engine, however, is very complicated.
The U.S. Pat. No. 3,701,238 discloses a grass cutting mechanism which has partly rotary and partly alternating characteristics, for which the energy supply is from a tractor because of the large energy requirement.
With the solution known from the French Patent No. 1,094,336, the vegetation stems are cut with shearing by the friction of moving blades and counter-blades rubbing against each other. With this solution the energy demand arising from the friction and the mechanical power transmission is similarly supplied by a tractor or internal combustion engine. A disadvantage is also the fact that because of the constant friction, the peripheral speed of the rotary blades can not be increased above 3-6 m/sec. This slows down the rate of work.
With these types of cutting mechanisms, the handling of the cut grass or produce after cutting, is not solved. The cut stems therefore pile up in front of the scythe and obstruct the forward movement of the cutter. A further disadvantage is that the long guiding tines utilized on such mechanisms, pierce the tree leaves lying on the grass, and as a result of this, the grass stems are bent down before cutting. As a result of this, blocking of the cutting mechanism can not be prevented. A disadvantage of the known solutions, is also the fact that the cutting mechanism is prone to damage, due to the low peripheral speed of 3-6 m/sec, relating to the low revolutions, the rotary blades are rigidly attached, and thus they cannot deviate in the case of obstruction.
The Hungarian patent No. 204,642 entitled "Procedure for energy saving cutting of stemmed plants, together with cutting mechanism", has counter-blades, and rotary blades with peripheral speed of 60-90 m/sec, fitted with 3.5 mm spacing between them and the counter-blades. With this solution, the energy required for cutting is low compared to the mowing system. At the same time, the high work rate characteristic of rotary cutters can be provided. The possibility of damage can be significantly reduced by articulated suspension of the blades.
A disadvantage of this solution is that fine cutting of the plant stems, that is good quality cutting, cannot be carried out, because due to the fixed cutting gap and the high peripheral speed of the rotary blades, the fine grass stems are not cut, but either torn or bent over the counter-blade. Tearing of the plant stems results is coarse injury, which heals up with difficulty. The part of the plant remaining in the soil, dries out by way of-the large injury, and only shoots out again with difficulty. The grass surface therefore becomes discolored and its condition deteriorates. In the case of cutting crop producing plants, the above mentioned injuries cause a reduction in crop, and even the danger of infection exists with the coarse injuries. It can accordingly be concluded that use of this type of machine could in practice be damaging to the environment.
A further disadvantage of the expounded solution, is that the high peripheral speed of the rotary blades, and the speed of revolution, ensuring the high, 60-90 m/sec peripheral speed, of the blade holder disc, is accompanied by a relatively high level of noise, which in many cases, for example, cutting of grass areas and parks of dwelling houses, hospitals and holiday resorts, can be extremely annoying and damaging to the environment.
Finally, a disadvantage is represented by the fact that fine and dense lawn grass, cannot be cue with this type of grass-cutter, because the surface of the counter-blades is excessively large and at the same time the free spaces between the counter-blades are excessively small and narrow. The ratio of the surface area of-the counter-blades and of the free spaces between them, in relation to each other, is one, or greater than one. Due to the narrowness of the free spacess, the grass stems will not go into the spaces, which results in the grass stems being bent over as the cutting mechanism moves forward. This results in patchy cutting, which spoils-the image by the stubble area left behind. As a consequence of this, in practice, in the case of fine dense lawn grass, cutting with the above mentioned machine can only be done at a low work rate.
The English Patent No. GB, A, 1 591 489 discloses a cutting mechanism, where the distance between the counter-blades and moving blades is 5 mm. In the interest of achieving a satisfactory cutting result at this spacing, a peripheral speed of a magnitude of about 80 m/s is necessary. With this solution, due to the 5 mm distance, the grass stems are not cut in the course of impact with the rotary blades, but they are layed over the cutting edges of the counter-blade and are broken off. Due to this, the rotary blades must overcome an increased resistance. Because of this increased resistance and the high peripheral speed, the energy requirement of these types of cutting mechanisms is fairly large. When an electric motor drive operated from an accumulator is used for driving of the rotary blades, the time which can be utilized for grass cutting is extremely short. Besides this, due to the high peripheral speed, the cutting mechanism is rather noisy.